Thermostable chimeric PQQ glucose dehydrogenase

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Abstract
The thermal stability of PQQ glucose dehydrogenases (PQQGDHs) which were chimeras with more than 95% made up of the N‐terminal region of Escherichia coli PQQGDH and the rest made up of the C‐terminal region of Acinetobacter calcoaceticus PQQGDHswas investigated. Among the chimeric PQQGDHs, E97A3 (E. coli 97% and A. calcoaceticus 3%) and E9545 were found to possess higher thermal stability than parental E. coli PQQGDH. Further detailed characterization of the thermal stability was carried out, focusing on E97A3. E97A3 showed a more than 3‐fold and 12‐fold increase in half life time at 40°C, compared with the PQQGDHs of E. coli and A. calcoaceticus, respectively. Using transition state theory, the increase in the free energy of inactivation observed in E97A3 was compared with those of the E. coli and A. calcoaceticus parental enzymes. The region responsible for this stabilization was also discussed.